Automotive alternator

ABSTRACT

A rear-end is constructed so as to have greater capacity than a front-end fan. The construction is such that a flow rate in a front-end ventilation pathway in which a cooling air flow enters through front-end air intake apertures is deflected centrifugally by the front-end fan and is then expelled through front-end air discharge apertures is greater a flow rate in a rear-end ventilation pathway in which a cooling air flow enters through rear-end air intake apertures is deflected centrifugally by the rear-end fan and is then expelled through rear-end air discharge apertures.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an automotive alternatorprovided with a blowing means.

[0003] The entire content of the basic Japanese Patent Application fromwhich the priority under the Convention is claimed in this applicationis hereby incorporated by reference into this application.

[0004] 2. Description of the Related Art

[0005]FIG. 25 is a cross section of a conventional automotivealternator, and FIGS. 26 and 27 are front elevations showing a front-endfan and a rear-end fan, respectively, used in a rotor of theconventional automotive alternator.

[0006] This automotive alternator is constructed by rotatably mounting aLundell-type rotor 7 by means of a shaft 6 inside a case 3 constructedfrom an aluminum front bracket 1 and an aluminum rear bracket 2, andfastening a stator 8 to an inner wall of the case 3 so as to cover anouter circumferential side of the rotor 7.

[0007] The shaft 6 is rotatably supported in the front bracket 1 and therear bracket 2. A pulley 4 is fastened to a first end of this shaft 6such that rotational torque from an engine can be transmitted to theshaft 6 by means of a belt (not shown).

[0008] Slip rings 9 for supplying electric current to the rotor 7 arefastened to a second end of the shaft 6, and a pair of brushes 10 arehoused in a brush holder 11 disposed inside the case 3 such that thepair of brushes 10 slide in contact with the slip rings 9. A regulator18 for adjusting the magnitude of alternating voltage generated in thestator 8 is fastened by adhesive to a heat sink 17 fitted onto the brushholder 11. A rectifier 12 which is electrically connected to the stator8 and converts alternating current generated in the stator 8 into directcurrent is mounted inside the case 3.

[0009] The rotor 7 is composed of a rotor coil 13 for generatingmagnetic flux on passage of electric current, and a pair of Lundell-typefront-end and rear-end pole cores 20 and 21 disposed so as to cover therotor coil 13, magnetic poles being formed in the front-end and rear-endpole cores 20 and 21 by magnetic flux generated in the rotor coil 13.The pair of front-end and rear-end pole cores 20 and 21 are made ofiron, each has a number of front-end and rear-end claw-shaped magneticpoles 22 and 23 disposed on an outer circumferential perimeter at evenpitch in a circumferential direction so as to project axially, and thefront-end and rear-end pole cores 20 and 21 are fastened to the shaft 6facing each other such that the front-end and rear-end claw-shapedmagnetic poles 22 and 23 intermesh.

[0010] The front-end and rear-end fans 5A and 5B are each prepared byform-working a metal plate, and each includes an annular fan baseportion 5 a, a number of blade base plates 5 b extending radiallyoutwards from outer peripheral portions of the fan base portions 5 a,and blades 5 c formed by folding and bending an outer peripheral portionof each of the blade base plates 5 b. The front-end and rear-end fans 5Aand 5B are fastened to front and rear axial ends of the front-end andrear-end pole cores 20 and 21, respectively.

[0011] The stator 8 is constituted by a stator core 15, and a statorcoil 16 formed by winding a conducting wire into this stator core 15,alternating current being generated in the stator coil 16 by changes inmagnetic flux from the rotor 7 accompanying rotation of the rotor 7.Portions of the stator coil 16 extend from front and rear axial ends ofthe stator core 15 and constitute a front-end coil end group 16 f and arear-end coil end group 16 r.

[0012] In automotive alternators constructed in this manner, electriccurrent is supplied from a battery (not shown) through the brushes 10and the slip rings 9 to the rotor coil 13, generating magnetic flux. Thefront-end claw-shaped magnetic poles 22 in the front-end pole core 20are magnetized with north-seeking (N) poles by this magnetic flux, andthe rear-end claw-shaped magnetic poles 23 in the rear-end pole core 21are magnetized with south-seeking (S) poles. At the same time,rotational torque from the engine is transmitted through the belt andthe pulley 4 to the shaft 6, rotating the rotor 7. Thus, a rotatingmagnetic field is applied to the stator coil 16, generatingelectromotive force in the stator coil 16. This alternatingelectromotive force passes through the rectifier 12 and is rectifiedinto direct current, the output thereof is adjusted by the regulator 18,and the battery is recharged.

[0013] In this automotive alternator, the rotor coil 13, the stator coil16, the rectifier 12, and the regulator 18 continuously generate heatduring power generation, and in an alternator having a rated outputcurrent in the 100A class, these components generate 60W, 500W, 120W,and 6W of heat energy, respectively, at rotational frequencies at whichthe temperature is high.

[0014] Thus, in order to cool the heat generated by power generation,front-end and rear-end air intake apertures 1 a and 2 a and front-endand rear-end air discharge apertures 1 b and 2 b are disposed in thefront bracket 1 and the rear bracket 2. More specifically, as shown inFIG. 25, a number of the front-end and rear-end air intake apertures 1 aand 2 a are disposed in lines circumferentially in axial surfaces (endsurfaces) of the front bracket 1 and the rear bracket 2, respectively,and a number of the front-end and rear-end air discharge apertures 1 band 2 b are disposed in lines circumferentially in radial surfaces (sidesurfaces) of the front bracket 1 and the rear bracket 2, respectively.

[0015] At the rear end, as indicated by arrows in FIG. 25, external airis sucked into the case 3 through the rear-end air intake apertures 2 aby rotation of the rear-end fans 5B, cooling the rectifier 12 and theregulator 18, and is then deflected centrifugally by the rear-end fans5B, cooling the rear-end coil end group 16 r of the stator coil 16before being expelled to the outside through the rear-end air dischargeapertures 2 b. At the same time, at the front end, as indicated byarrows in FIG. 25, external air is sucked into the case 3 through thefront-end air intake apertures 1 a by rotation of the front-end fans 5Aand is then deflected centrifugally by the front-end fans 5A, coolingthe front-end coil end group 16 f of the stator coil 16 before beingexpelled to the outside through the front-end air discharge apertures 1b. In addition, a cooling air flow flows from the front end to the rearend as a result of a pressure difference between the front end and therear end, cooling the rotor coil 13.

[0016] When the conventional automotive alternator constructed in thismanner is operated at a rotational frequency of 5000 rpm, the air flowrate in each of the ventilation pathways has been such that thefront-end intake air flow rate Qf_(IN) was 0.025 m³/s, the front-enddischarge air flow rate Qf_(ouT) was 0.02 m³/s, the rear-end intake airflow rate Qr_(IN) was 0.03 m³/s, the rear-end discharge air flow rateQr_(OUT) was 0.035 m³/s, and the front-to-rear air flow rate Q_(f→r) was0.005 m³/s.

[0017] This conventional automotive alternator is constructed such thatthe rear-end flow rates are greater than the front-end flow rates. Thus,at the rear end, because the large volume of cooling air taken inthrough the rear-end air intake apertures 2 a is warmed as it cools therectifier 12 and the regulator 18 and is then supplied for the coolingof the rear-end coil end group 16 r of the stator coil 16, temperatureincreases in the rear-end coil end group 16 r cannot be sufficientlysuppressed. Similarly, at the front end, because the small volume ofcooling air taken in through the front-end air intake apertures 1 a issupplied for the cooling of the front-end coil end group 16 f of thestator coil 16, temperature increases in the front-end coil end group 16f cannot be sufficiently suppressed. In other words, one problem hasbeen that overall cooling efficiency has been low because the front-endflow rates have been too low to effectively cool the stator coil 16.

[0018] Now, fan-generated noise (SPL: Sound Pressure Level) is expressedby SPL=k+10 log(P²⁵×Q), and is significantly affected by pressure loss Pand by flow rate Q at the work point. Moreover, k is the specific soundlevel, being the noise per unit pressure and flow rate.

[0019] The relationship between pressure loss (P), flow rate (Q), andwind resistance (r) is generally expressed by P=r×Q².

[0020] Thus, in the case of an identical flow rate, pressure lossbecomes increasingly excessive as wind resistance increases, causing SPLto worsen significantly.

[0021] Consequently, another problem in conventional automotivealternators has been that noise is increased because the flow rates inthe rear end where the wind resistance is higher are greater than in thefront end, as mentioned above.

SUMMARY OF THE INVENTION

[0022] The present invention aims to solve the above problems and anobject of the present invention is to provide an automotive alternatorenabling overall cooling efficiency to be raised by making front-endflow rates capable of effectively cooling coil ends of a stator coilgreater than rear-end flow rates so that the stator coil can be cooledsufficiently, and increasing the capacity of a rear-end blowing meansrelative to the capacity of a front-end blowing means to ensure rear-endflow rates so that a rectifier and a regulator are sufficiently cooled,and in addition, enabling noise to be reduced by making the flow ratesin the front end, where wind resistance is small, greater than the flowrates in the rear end, where wind resistance is great.

[0023] In order to achieve the above object, according to one aspect ofthe present invention, there is provided an automotive alternatorincluding:

[0024] a rotor fastened to a shaft rotatably supported by a frontbracket and a rear bracket, the rotor having a pair of Lundell-type polecores disposed inside the brackets;

[0025] a stator supported by the brackets, the stator being disposed soas to cover an outer circumference of the rotor, the stator comprising:

[0026] a cylindrical stator core in which a plurality of slots havinggrooves lying in an axial direction are disposed circumferentially so asto open onto an inner circumferential side; and

[0027] a stator coil installed in the stator core so as to constitute apredetermined winding construction;

[0028] a pulley fastened to a front end of the shaft; and

[0029] a rectifier disposed at a rear end of the rotor,

[0030] wherein

[0031] a plurality of front-end and rear-end air intake apertures aredisposed in axial end surfaces of the front and rear brackets,respectively;

[0032] a plurality of front-end and rear-end air discharge apertures aredisposed in radial side surfaces of the front and rear brackets,respectively; and

[0033] front-end and rear-end blowing means are disposed at front andrear axial ends of the rotor, respectively,

[0034] whereby a front-end ventilation pathway in which a cooling airflow flows through the front-end air intake apertures into the front-endbracket and flows out through the front-end air discharge apertures, arear-end ventilation pathway in which a cooling air flow flows throughthe rear-end air intake apertures into the rear-end bracket and flowsout through the rear-end air discharge apertures, and a front-to-rearventilation pathway in which a cooling air flow flows through an innerside of the rotor between the front end and the rear end each isgenerated by operation of the blowing means,

[0035] wherein a capacity of the rear-end blowing means is greater thana capacity of the front-end blowing means, and a front-end air intakeflow rate is greater than a rear-end air intake flow rate.

[0036] A front-end air discharge flow rate may be greater than arear-end air discharge flow rate.

[0037] According to another aspect of the present invention, there isprovided an automotive alternator including:

[0038] a rotor fastened to a shaft rotatably supported by a frontbracket and a rear bracket, the rotor having a pair of Lundell-type polecores disposed inside the brackets;

[0039] a stator supported by the brackets, the stator being disposed soas to cover an outer circumference of the rotor, the stator comprising:

[0040] a cylindrical stator core in which a plurality of slots havinggrooves lying in an axial direction are disposed circumferentially so asto open onto an inner circumferential side; and

[0041] a stator coil installed in the stator core so as to constitute apredetermined winding construction;

[0042] a pulley fastened to a front end of the shaft; and

[0043] a rectifier disposed at a rear end of the rotor, wherein

[0044] a plurality of front-end and rear-end air intake apertures aredisposed in axial end surfaces of the front and rear brackets,respectively;

[0045] a plurality of front-end and rear-end air discharge apertures aredisposed in radial side surfaces of the front and rear brackets,respectively; and

[0046] front-end and rear-end blowing means are disposed at front andrear axial ends of the rotor, respectively,

[0047] whereby a front-end ventilation pathway in which a cooling airflow flows through the front-end air intake apertures into the front-endbracket and flows out through the front-end air discharge apertures, arear-end ventilation pathway in which a cooling air flow flows throughthe rear-end air intake apertures into the rear-end bracket and flowsout through the rear-end air discharge apertures, and a front-to-rearventilation pathway in which a cooling air flow flows through an innerside of the rotor between the front end and the rear end each isgenerated by operation of the blowing means,

[0048] wherein a capacity of the rear-end blowing means is greater thana capacity of the front-end blowing means, and a front-end air dischargeflow rate is greater than a rear-end air discharge flow rate.

[0049] The front-to-rear ventilation pathway may be blocked.

[0050] The front-end and rear-end blowing means may be the Lundell-typepole cores or fans.

[0051] The front-end blowing means may be one of the Lundell-type polecores and the rear-end blowing means may be a fan.

[0052] The front-end and rear-end blowing means may be fans, each fancomprising:

[0053] a generally annular fan base portion;

[0054] a plurality of blade base plates extending radially outwards fromouter circumferential edge portions of the fan base portion; and

[0055] a plurality of blades standing on an outer circumferential edgeportion of each of the plurality of blade base plates.

[0056] The rear-end fan may be provided with a greater number of bladesthan the front-end fan.

[0057] A maximum blade height of the rear-end fan may be greater than amaximum blade height of the front-end fan.

[0058] The blade base plates of the rear-end fan may be formed into ashape which blocks valley portions between adjacent magnetic poles ofthe rotor.

[0059] A shielding plate may be disposed for blocking air gaps formed bythe blade base plates of the rear-end fan and valley portions betweenadjacent magnetic poles of the rotor.

[0060] The stator coil may be constructed by:

[0061] inserting coil segments composed of short conductors formed intoa general U shape from a first end of the stator core into slot pairs inwhich the slots in each pair are a predetermined number of slots apart;and

[0062] circumferentially bending and joining together free end portionsof the coil segments extending outwards at a second end of the statorcore from slots the predetermined number of slots apart so as toconstitute the predetermined winding construction,

[0063] wherein turn-end coil ends formed by U-shaped turn ends of thecoil segments are aligned in rows circumferentially to constitute aturn-end coil end group, and joint-end coil ends formed by the joiningof the free end portions of the coil segments are aligned in rowscircumferentially to constitute a joint-end coil end group.

[0064] The joint-end coil end group of the stator coil may be disposedat the front end of the stator core.

[0065] The stator coil may be constructed by linking a plurality ofwinding sub-portions so as to constitute the predetermined windingconstruction,

[0066] wherein each of the winding sub-portions is constituted by onestrand of wire constituted by a large number of straight portions housedinside the slots and a large number of turn portions linking togetherend portions adjacent straight portions outside the slots, the strand ofwire being installed in the stator core by housing the straight portionsso as to form different layers relative to a slot depth direction inslots the predetermined number of slots apart, and coil ends formed bythe turn portions are aligned in rows circumferentially to constitutefront-end and rear-end coil end groups of the stator coil.

BRIEF DESCRIPTION OF THE DRAWINGS

[0067]FIG. 1 is a cross section of a construction of an automotivealternator according to Embodiment 1 of the present invention;

[0068]FIG. 2 is a graph of blowing performance of fans used in theautomotive alternator according to Embodiment 1 of the presentinvention;

[0069]FIG. 3 is a perspective of a coil segment used in a stator of theautomotive alternator according to Embodiment 1 of the presentinvention;

[0070]FIG. 4 is a partial side elevation of the stator with the coilsegments installed;

[0071]FIG. 5 is a partial perspective of the stator with the coilsegments installed;

[0072]FIG. 6 is a perspective of a rotor according to Inventive Example1 of the present invention;

[0073]FIG. 7 is a front elevation of a front-end fan according toInventive Example 1 of the present invention;

[0074]FIG. 8 is a front elevation of a rear-end fan according toInventive Example 1 of the present invention;

[0075]FIG. 9 is a cross section of a rotor according to InventiveExample 2 of the present invention;

[0076]FIG. 10 is a perspective of a rotor according to Inventive Example3 of the present invention;

[0077]FIG. 11 is a front elevation of a front-end fan according toInventive Example 4 of the present invention;

[0078]FIG. 12 is a front elevation of a rear-end fan according toInventive Example 4 of the present invention;

[0079]FIG. 13 is a front elevation of a front-end fan according toInventive Example 5 of the present invention;

[0080]FIG. 14 is a front elevation of a rear-end fan according toInventive Example 5 of the present invention;

[0081]FIG. 15 is a front elevation of a mounted state of a rear-end fanaccording to Inventive Example 6 of the present invention;

[0082]FIG. 16 is a perspective of a front-end pole core according toInventive Example 9 of the present invention;

[0083]FIG. 17 is a perspective of a rear-end pole core according toInventive Example 9 of the present invention;

[0084]FIG. 18 is a partial cross section of an automotive alternatoraccording to Embodiment 2 of the present invention;

[0085]FIG. 19 is a perspective of a stator used in an automotivealternator according to Embodiment 3 of the present invention;

[0086]FIG. 20A is an end elevation of a winding assembly constituting astator coil in the stator of the automotive alternator according toEmbodiment 3 of the present invention;

[0087]FIG. 20B is a plan of the winding assembly constituting the statorcoil in the stator of the automotive alternator according to Embodiment3 of the present invention;

[0088]FIG. 21 is a perspective of part of a strand of wire constitutingthe stator coil in the stator of the automotive alternator according toEmbodiment 3 of the present invention;

[0089]FIG. 22 is a diagram explaining an arrangement of the strands ofwire constituting the stator coil in the stator of the automotivealternator according to Embodiment 3 of the present invention;

[0090]FIG. 23 is an end elevation explaining connections in one statorcoil phase portion in the stator of the automotive alternator accordingto Embodiment 3 of the present invention;

[0091]FIG. 24 is a circuit diagram of the stator of the automotivealternator according to Embodiment 3 of the present invention;

[0092]FIG. 25 is a cross section of a construction of a conventionalautomotive alternator;

[0093]FIG. 26 is a front elevation of a conventional front-end fan; and

[0094]FIG. 27 is a front elevation of a conventional rear-end fan.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0095] The preferred embodiments of the present invention will now beexplained with reference to the drawings.

Embodiment 1

[0096]FIG. 1 is a cross section of a construction of an automotivealternator according to Embodiment 1 of the present invention, FIG. 2 isa graph of blowing performance of fans used in the automotive alternatoraccording to Embodiment 1 of the present invention, FIG. 3 is aperspective of a U-shaped coil segment constituting a stator coil usedin a stator of the automotive alternator according to Embodiment 1 ofthe present invention, FIG. 4 is a partial side elevation of the statorwith the coil segments installed, and FIG. 5 is a partial perspective ofthe stator with the coil segments installed. Moreover, in each of thefigures, portions which are identical or correspond to portions of theconventional automotive alternator shown in FIG. 25 will be givenidentical numbering and explanation thereof will be omitted.

[0097] In each of the figures, a front-end fan 40 functioning as afront-end blowing means is fastened to a front-end surface of thefront-end pole core 20 of the rotor 7, and a rear-end fan 41 functioningas a rear-end blowing means is fastened to a rear-end surface of therear-end pole core 21 of the rotor 7. The front-end fan 40 has a blowingperformance indicated by a curve A1 in FIG. 2, and the rear-end fan 41has a blowing performance indicated by a curve A2 in FIG. 2. In otherwords the rear-end fan 41 has a greater capacity than the front-end fan40. Moreover, the capacity of each fan is defined as the magnitude of apressure difference upstream and downstream from the fan for apredetermined flow rate, capacity being to be considered greater if theresulting pressure difference is greater for an identical flow rate.

[0098] A stator 35 is constituted by a stator core 15 and a stator coil36. The stator coil is formed into a cylindrical shape, a plurality ofteeth 15 a having a generally rectangular cross-sectional shape aredisposed at even angular pitch in a circumferential direction so as toprotrude radially inwards, and slots 15 b for housing the stator coil 36are formed between the teeth 15 a. Each of the slots 15 b has grooveslying parallel to an axial direction, and is open on an innercircumferential side.

[0099] The stator coil 36 is constructed by connecting a large number ofshort coil segments 30 so as to form a predetermined windingconstruction, for example, a three-phase alternating-current windingconstruction. A conductor such as copper having a rectangular crosssection covered with an electrically-insulating coating is used for thecoil segments 30, and each coil segment 30 is formed into a general Ushape composed of a pair of straight portions 30 a linked by a generallyV-shaped turn portion 30 b. Furthermore, each of the coil segments 30 isprepared such that the spacing between the pair of straight portions 30a is adjusted in advance to a spacing of three slots. The pairs ofstraight portions 30 a of the coil segments 30 are inserted from therear end of the stator core 15 into a set of pairs of slots 15 b inwhich the slots in each pair are three slots away from each other,extending portions of the straight portions 30 a extending outwards atthe front end of the stator core 15 are bent, and then free end portions30 c are joined to each other so as to form one three-phasealternating-current winding overall, for example. Moreover, the set ofpairs of slots 15 b in which the slots in each pair are three slots awayfrom each other corresponds to a set of slots including a first slot anda fourth slot in a circumferential direction, for example.

[0100] Here, these coil segments 30 are inserted two at a time into eachof the sets of slots 15 b such that a height dimension of the turnportions 30 b is aligned as shown in FIG. 4. Four straight portions 30 aare housed in each of the slots 15 b so as to line up in one rowradially with a longitudinal direction of their rectangular crosssections aligned radially.

[0101] In each of the sets of slots 15 b, a first coil segment 30 isinserted into a first position from an outer circumferential side of afirst slot 15 b and a second position from the outer circumferentialside of a second slot 15 b, and a second coil segment 30 is insertedinto a third position from the outer circumferential side of the firstslot 15 b and a fourth position from the outer circumferential side ofthe second slot 15 b. An outer-layer winding is prepared by joining freeend portions 30 c of the coil segments 30 inserted into the firstpositions from the outer circumferential side of the slots 15 b to freeend portions 30 c of other coil segments 30 inserted into the secondpositions from the outer circumferential side of slots 15 b three slotsaway. An inner-layer winding is prepared by joining free end portions 30c of the coil segments 30 inserted into the third positions from theouter circumferential side of the slots 15 b to free end portions 30 cof other coil segments 30 inserted into the fourth positions from theouter circumferential side of slots 15 b three slots away. Then, theouter-layer winding and the inner-layer winding are connected in series.

[0102] The free end portions 30 c of the coil segments 30 are stackedradially and joined to each other by generally fusing joint portions(tip portions of the free end portions 30 c) by arc welding. The twojoined free end portions 30 c (joint portions 31) in the inner-layerwinding and the two joined free end portions 30 c (joint portions 31) inthe outer-layer winding are lined up in one row radially. Thus,joint-end coil ends 32 a constituted by the joint portion 31 ends of thecoil segments 30 are arranged in two rows circumferentially toconstitute a joint-end coil end group 32.

[0103] At this time, the two free end portions 30 c being joined arestacked together with the short sides of the rectangular cross sectionsthereof abutted, and are joined by fusing the whole of the tip portionsby arc welding.

[0104] Turn-end coil ends 33 a formed by the turn portion 30 b ends ofthe coil segments 30 are arranged in two rows circumferentially toconstitute a turn-end coil end group 33.

[0105] The stator 35 constructed in this manner is installed in anautomotive alternator with the joint-end coil end group 32 constructedby joining the free end portions 30 c of the coil segments 30 positionedat a front end and the turn-end coil end group 33 constituted by theturn portions 30 b positioned at a rear end. In other words, thejoint-end coil end group 32 of the stator coil 36 corresponds to afront-end coil end group 36 f, and the turn-end coil end group 33corresponds to a rear-end coil end group 36 r.

[0106] Next, the work points of the fans 40 and 41 according toEmbodiments 1 will be explained with reference to FIG. 2. In FIG. 2, A1is a blowing performance curve for the front-end fan 40, A2 is a blowingperformance curve for the rear-end fan 41, Rf is an air flow passagepressure loss curve for the ventilation pathways in the front end, andRr is an air flow passage pressure loss curve for the ventilationpathways in the rear end.

[0107] From FIG. 2, the work point of the front-end fan 40 is theintersection between the curve A1 and the curve Rf, and the work pointof the rear-end fan 41 is the intersection between the curve A2 and thecurve Rr. In other words, a front-end air flow rate Q3 and a front-endair flow pressure P3 are achieved by the front-end fan 40, and arear-end air flow rate Q2 and a rear-end air flow pressure P2 areachieved by the rear-end fan 41. Moreover, Q2 is less than Q3 (Q2<Q3),and P2 is greater than P3 (P2>P3).

[0108] Thus, the front-end air flow rate of the cooling air flow flowingthrough the front-end ventilation pathway, in which air enters the frontbracket 1 through the front-end air intake apertures 1 a, is deflectedcentrifugally by the front-end fan 40, and is then expelled through thefront-end air discharge apertures 1 b, is greater than the rear-end airflow rate of the cooling air flow flowing through the rear-endventilation pathway, in which air enters the rear bracket 2 through therear-end air intake apertures 2 a, is deflected centrifugally by therear-end fan 40, and is then expelled through the rear-end air dischargeapertures 2 b. Furthermore, a portion of the cooling air flow enteringthe front end flows to the rear end through the inside of the rotor 7.

[0109] Here, “air flow pressure” means the difference between thepressure generated in front of a resistant member disposed in thecooling air flow created by operation of the fan and that generatedbehind the resistant member. The greater the air flow pressure, thegreater the capacity of the fan is enhanced.

[0110] Now, if fans having the blowing performance curve A1 are used forthe fans in both the front end and the rear end, the work points of thefront-end and rear-end fans are (Q3, P3) and (Q1, P1), respectively.Moreover, Q1<Q2<Q3, and P2>P1 >P3.

[0111] When a fan having the blowing performance curve A2 is used forthe rear-end fan 41, the work point of the rear-end fan 41 is (Q2, P2).In other words, by increasing the capacity of the rear-end fan 41, therear-end air flow rate can be raised from Q1 to Q2. In this case, thecapacity of the rear-end fan 41 is set such that the rear-end air flowrate does not exceed the front-end air flow rate.

[0112] In this manner, in Embodiment 1, the front-end air flow rate isgreater than the rear-end air flow rate, and the capacity of therear-end fan 41 is greater than the capacity of the front-end fan 40.

[0113] Because the front-end air flow rate capable of effectivelycooling the coil end group of the stator coil 36 is greater than therear-end air flow rate, the stator coil 36 can be sufficiently cooled,enabling temperature increases in the stator coil 36 to be suppressed.In addition, because the capacity of the rear-end fan 41 is greater thanthe capacity of the front-end fan 40, the rear-end air flow rate issufficiently ensured and the rectifier 12 and the regulator 18 can besufficiently cooled, enabling temperature increases in the rectifier 12and the regulator 18 to be suppressed. Consequently, the automotivealternator obtained enables overall cooling efficiency to be raised.

[0114] In addition, because the air flow rate at the front end wherewind resistance is small is made greater than the air flow rate at therear end where wind resistance is great, the automotive alternatorobtained enables worsening of wind noise to be suppressed.

[0115] Because the stator coil 36 is constructed by connecting a largenumber of short coil segments 30 having a rectangular cross section, thespace factor of the coil segments 30 relative to the slots 15 b can beraised, enabling the achievement of increased output.

[0116] Because the coil segments 30 are formed into the general U shape,the stator coil 36 obtained can be installed in the stator core byinserting the coil segments into the slots 15 b from a first end of thestator core 15 and joining together the free end portions 30 c extendingoutwards at a second end of the stator core 15. Thus, the stator coil 36installed in the stator core 15 can be prepared easily.

[0117] Because the joint-end coil end group 32 has joint portions 31 inwhich heat dissipation is raised by removing the electrically-insulatingcoating and is disposed at the front end where the air flow rate islarge, heat from the stator coil 36 is efficiently dissipated from thejoint-end coil end group 32, effectively suppressing temperatureincreases in the stator coil 36.

[0118] The fan construction used in the automotive alternator accordingto the present invention will now be explained in detail.

Inventive Example 1

[0119]FIG. 6 is a perspective of Inventive Example 1 of a rotor used inthe automotive alternator of the present invention, and FIGS. 7 and 8are front elevations of a front-end fan 40A and a rear-end fan 41A,respectively, used in the rotor shown in FIG. 6.

[0120] The front-end and rear-end fans 40A and 41A were formed byworking a thin metal sheet and were constituted by: annular fan baseportions 40 a and 41 a; a number of blade base plates 40 b and 41 bextending radially outwards from outer circumferential edge portions ofthe fan base portions 40 a and 41 a; and blades 40 c and 41 c formed byfolding an outer circumferential edge portion of each of the blade baseplates 40 b and 41 b. Outside diameters (Df and Dr), numbers of blades(Nf and Nr), and blade heights (BHf and BHr) were the same for each ofthe fans 40A and 41A, but a blade chord length (BLr) of the rear-end fan41A was formed so as to be longer than a blade chord length (BLf) of thefront-end fan 40A, making the capacity of the rear-end fan 41A greaterthan the capacity of the front-end fan 40A. That is, Df=Dr, Nf=Nr,BHf=BHr, and BLf<BLr.

[0121] When an automotive alternator fitted with a rotor mounted withthe fans 40A and 41A constructed in this manner was operated at arotational frequency of 5000 rpm, the front-end intake air flow rateQf_(IN) was 0.05 m³/s, the front-end discharge air flow rate Qf_(OUT)was 0.048 m³/s, the rear-end intake air flow rate Qr_(IN) was 0.033m³/s, the rear-end discharge air flow rate Qr_(OUT) was 0.035 m³/s, andthe front-to-rear air flow rate Q_(f→r) was 0.002 m³/s.

[0122] According to Inventive Example 1, because the blade chord length(BLr) of the rear-end fan 41A were formed so as to be longer than theblade chord length (BLf) of the front-end fan 40A, the capacity of therear-end fan 41A was greater than the capacity of the front-end fan 40A,and in addition, the front-end intake air flow rate Qf_(IN) and thefront-end discharge air flow rate Qf_(OUT) were greater than therear-end intake air flow rate Qr_(IN) and the rear-end discharge airflow rate Qr_(OUT).

[0123] Consequently, the effects of Embodiment 1 above were achieved.

[0124] Furthermore, because the number of blades in each of thefront-end and rear-end fans 40A and 41A was ten, the front-end andrear-end air flow rates were increased compared to the conventionalexample in which the number of blades was eight, enabling temperatureincreases in the stator coil 36, the rectifier 12, and the regulator 18to be suppressed further.

Inventive Example 2

[0125] As shown in FIG. 9, in Inventive Example 2, the blade height(BHr) of a rear-end fan 41B was formed so as to be higher than the bladeheight (BHf) of a front-end fan 40B. Moreover, the rest of theconstruction was the same as in Inventive Example 1.

[0126] When an automotive alternator fitted with a rotor mounted withthe fans 40B and 41B constructed in this manner was operated at arotational frequency of 5000 rpm, the front-end intake air flow rateQf_(IN) was 0.05 m³/s, the front-end discharge air flow rate Qf_(OUT)was 0.045 m³/s, the rear-end intake air flow rate Qr_(IN) was 0.038m³/s, the rear-end discharge air flow rate Qr_(OUT) was 0.043 m³/s, andthe front-to-rear air flow rate Q_(f→r) was 0.005 m³/s.

[0127] In Inventive Example 2, the front-end intake air flow rateQf_(IN) and the front-end discharge air flow rate Qf_(OUT) were alsogreater than the rear-end intake air flow rate Qr_(IN) and the rear-enddischarge air flow rate Qr_(OUT).

[0128] Furthermore, in Inventive Example 2, because the blade height(BHr) of the rear-end fan 41B was formed so as to be higher than theblade height (BHf) of the front-end fan 40B, the capacity of therear-end fan 41B was even greater than the capacity of the front-end fan40B, making the rear-end intake air flow rate Qr_(IN) and the rear-enddischarge air flow rate Qr_(OUT) greater than in Inventive Example 1above.

[0129] Thus, temperature increases in the rectifier 12 and the regulator18 were suppressed further than in Inventive Example 1.

Inventive Example 3

[0130] As shown in FIG. 10, a shielding plate 42 was mounted between therear-end fan 41B and the rear-end pole core 21, blocking air gaps formedby valley portions between the rear-end claw-shaped magnetic poles 23and by the blade base plates 41 b. Moreover, the rest of theconstruction was the same as in Inventive Example 2.

[0131] When an automotive alternator fitted with a rotor constructed inthis manner was operated at a rotational frequency of 5000 rpm, thefrontend intake air flow rate Qf_(IN) was 0.05 m³/s, the front-enddischarge air flow rate Qf_(OUT) was 0.05 m³/s, the rear-end intake airflow rate Qr_(IN) was 0.045 m³/s, the rear-end discharge air flow rateQr_(OUT) was 0.045 m³/s, and the front-to-rear air flow rate Q_(f→r)was0 m³/s.

[0132] In Inventive Example 3, the front-end intake air flow rateQf_(IN) and the front-end discharge air flow rate Qf_(OUT) were alsogreater than the rear-end intake air flow rate Qr_(IN) and the rear-enddischarge air flow rate Qr_(OUT).

[0133] Because the ventilation pathway of the cooling air flow flowingfrom the front-end to the rear-end was blocked by the shielding plate42, the front-to-rear air flow rate Q_(f→r) was eliminated. Thus,because the front-end intake air flow rate Qf_(IN) was able tocontribute to the cooling of the front-end coil end group without loss,temperature increases in the stator coil 36 could be reliablysuppressed. Because the spaces formed between the blade base plates 41 bwere blocked by the shielding plate 42, the capacity of the rear-end fan41B was raised further, increasing the rear-end intake air flow rateQr_(IN), thereby enabling temperature increases in the rectifier 12 andthe regulator 18 to be reliably suppressed.

Inventive Example 4

[0134] As shown in FIGS. 11 and 12, in Inventive Example 4, a front-endfan 40C and a rear-end fan 41C had identical outside diameters (Df andDr), blade heights (BHf and BHr), and blade chord lengths (BLf and BLr),the number of blades (Nf) in the front-end fan 40C was eight, and thenumber of blades (Nr) in the rear-end fan 41C was ten. That is, Df=Dr,Nf<Nr, BHf=BHr, and BLf=BLr.

[0135] Consequently, in Inventive Example 4, because a fan having agreater number of blades than the number of blades in the front-end fan40C was used for the rear-end fan 41C, the capacity of the rear-end fan41C was also greater than the capacity of the front-end fan 40C,enabling the effects of Embodiment 1 above to be achieved.

Inventive Example 5

[0136] As shown in FIGS. 13 and 14, in Inventive Example 5, a front-endfan 40D and a rear-end fan 41D had identical outside diameters (Df andDr), blade heights (BHf and BHr), and numbers of blades (Nf and Nr), andthe blade chord length (BLr) of the rear-end fan 41D was formed so as tobe longer than the blade chord length (BLf) of the front-end fan 40D.That is, Df=Dr, Nf=Nr, BHf=BHr, and BLf<BLr.

[0137] Consequently, in Inventive Example 5, because a fan having alonger blade chord length than the blade chord length of the front-endfan 40D was used for the rear-end fan 41D, the capacity of the rear-endfan 41C was also greater than the capacity of the front-end fan 40C,enabling the effects of Embodiment 1 above to be achieved.

Inventive Example 6

[0138] As shown in FIG. 15, in Inventive Example 6, the blade baseplates 41 b of a rear-end fan 41E were enlarged, and the rear-end fan41E were fastened to the rear-end pole core 21 such that the enlargedblade base plates 41 b covered the valley portions between adjacentrear-end claw-shaped magnetic poles 23. Moreover, the rest of theconstruction was the same as in Inventive Example 5.

[0139] In Inventive Example 6, because the valley portions betweenadjacent rear-end claw-shaped magnetic poles 23 were blocked by theblade base plates 41 b when viewed axially, the front-to-rear air flowrate Q_(f→r) was limited. Thus, because the front-end intake air flowrate Qf_(IN) was able to contribute to the cooling of the front-end coilend group with limited loss, temperature increases in the stator coil 36could be further suppressed. Because the spaces formed between the bladebase plates 41 b were blocked by end surfaces of the rear-endclaw-shaped magnetic poles 23, the capacity of the rear-end fan 41E wasraised further, increasing the rear-end intake air flow rate Qr_(IN),thereby enabling temperature increases in the rectifier 12 and theregulator 18 to be reliably suppressed.

Inventive Example 7

[0140] In Inventive Example 7, an outside diameter of a front-end fan 40was formed so as to be smaller than an outside diameter of a rear-endfan 41. Moreover, the rest of the construction was the same as inInventive Example 5.

[0141] Consequently, in Inventive Example 7, because a fan having asmaller outside diameter than the outside diameter of the rear-end fan41 was used for the front-end fan 40, the capacity of the rear-end fan41 was also greater than the capacity of the front-end fan 40, enablingthe effects of Embodiment 1 above to be achieved.

Inventive Example 8

[0142] In each of the above inventive examples, fans 40 and 41 were usedas the front-end and rear-end blowing means, but in Inventive Example 8,the front-end pole core 20 was used as the front-end blowing means and arear-end fan 41 was used as the rear-end blowing means.

[0143] Here, because the capacity of the front-end pole core 20 as ablowing means was small compared to the rear-end fan 41, the capacity ofthe rear-end blowing means was also greater than the capacity of thefront-end blowing means in Inventive Example 8, enabling the sameeffects to be achieved.

[0144] Furthermore, because the front-end fan was eliminated, costscould be reduced.

Inventive Example 9

[0145] In Inventive Examples 1 to 7 above, fans 40 and 41 were used asthe front-end and rear-end blowing means, but in Inventive Example 9,the front-end and rear-end pole cores 20 and 21 were used as thefront-end and rear-end blowing means.

[0146] In Inventive Example 9, as shown in FIG. 16, front-end shoulderportions 22 a were formed on the claw-shaped magnetic poles 22 of thefront-end pole core 20 in an inclined plane having a predetermined anglerelative to a front-end end surface of the front-end pole core 20 andintersecting the front-end end surface of the front-end pole core 20 ona circle centered on th e axial center of the front-end pole core 20. Onthe other hand, as shown in FIG. 17, rear-end shoulder portions 23 awere formed on the claw-shaped magnetic poles 23 of the rear-end polecore 21 in an inclined plane having a predetermined angle relative to arear-end end surface of the rear-end pole core 21 and having a line ofintersection with the rear-end end surface of the rear-end pole core 21which gradually approached the axial center of the rear-end pole core 21backwards relative to the direction of rotation.

[0147] Thus, due to the differences in the shapes of the shoulderportions 22 a and 23 a of the front-end and rear-end claw-shapedmagnetic poles 22 and 23, the capacity of the rear-end pole core 21 as ablowing means was greater than the capacity of the front-end pole core20 as a blowing means, enabling the fans 40 and 41 to be dispensed with,thereby enabling costs to be reduced further.

Embodiment 2

[0148] As shown in FIG. 18, in Embodiment 2, the stator 35 is disposedsuch that a front-end axial height (CLf) of the front-end coil end group36 f of the stator coil 36 is greater than a rear-end axial height (CLr)of the rear-end coil end group 36 r, and a front-end axial overlap (Of)between the front-end coil end group 36 f and the front-end fan 40 isgreater than a rear-end axial overlap (Or) between the rear-end coil endgroup 36 r and the rear-end fan 41. In other words, CLr<CLf and Or<OfMoreover, the rest of the construction is the same as in Embodiment 1.

[0149] According to Embodiment 2, the stator 35 is disposed such thatthe front-end axial height (CLf) of the front-end coil end group 36 f ofthe stator coil 36 is greater than the rear-end axial height (CLr) ofthe rear-end coil end group 36 r. Thus, the volume of the coil end groupexposed to the cooling air flow is limited in the rear end where coolingefficiency is poor, and the volume of the coil end group exposed to thecooling air flow is increased in the front end where cooling efficiencyis good, cooling the stator coil 36 effectively.

[0150] The stator 35 is also disposed such that the front-end axialoverlap (Of) between the front-end coil end group 36 f and the front-endfan 40 is greater than the rear-end axial overlap between the rear-endcoil end group 36 r and the rear-end fan 41. Thus, the volume of thecoil end group exposed to the cooling air flow is increased in the frontend where cooling efficiency is good, cooling the stator coileffectively.

[0151] Naturally, the overall cooling efficiency can be raised furtherand noise can be significantly decreased in Embodiment 2 as well byadopting the constructions from any of Inventive Examples 1 to 9 above.

[0152] Moreover, in Embodiments 1 and 2 above, the coil segments 30 usedwere formed into a general U shape, but the present invention is notlimited to coil segments 30 formed into a general U shape; the coilsegments may be short conductor segments extending linearly.

Embodiment 3

[0153] In Embodiments 1 and 2 above, the stator coil was constructed byjoining a large number of short coil segments 30 so as to adopt apredetermined overall winding construction, but in Embodiment 3, thestator coil is constructed so as to adopt a predetermined overallwinding construction by linking a plurality of winding sub-portions eachformed by installing one strand of wire composed of continuous wire intothe stator core.

[0154]FIG. 19 is a perspective of a stator of an automotive alternatoraccording to Embodiment 3 of the present invention. Connecting portionssuch as crossover-connections have been omitted from the diagram tofacilitate explanation.

[0155] In FIG. 19, the stator 81 includes: a stator core 50 composed ofa cylindrical laminated core in which a plurality of teeth 50 a having agenerally rectangular cross sectional shape are disposed at even pitchin a circumferential direction so as to protrude radially inwards, slots50 b extending axially being formed between the teeth 50 a; a statorcoil 51 installed in the stator core 50; and insulators 52 mounted inthe slots 50 b for electrically insulating the stator coil 51 from thestator core 50. The stator coil 51 includes front-end and rear-end coilend groups 51 f and 51 r which extend outwards at a front end and a rearend of the stator core 50.

[0156] Furthermore, the stator coil 51 is provided with two windingassemblies 60 disposed in two rows radially. The winding assemblies 60are each constituted by two winding sub-portions in each of which onestrand of wire 61 is folded over outside the slots 50 b at end surfacesof the stator core 50 and wound into a wave winding so as to alternatelyoccupy an inner layer and an outer layer in a slot depth directionwithin slots 50 b a predetermined number of slots apart. In this case,the stator core 50 is formed with ninety-six slots 50 b at even pitch soas to house two three-phase stator winding groups 53 (described below)such that the number of slots housing the two three-phase stator windinggroups 53 corresponds to the number of magnetic poles (sixteen) in therotor 7. In other words, the number of slots per phase per pole is two.Continuous wire of a copper wire material having a flat cross sectioncoated with an electrically-insulating coating, for example, is used inthe strands of wire 61.

[0157] The construction of the winding assemblies 60 will be explainedhere in detail with reference to FIGS. 20A to 22. FIG. 20A is an endelevation of a winding assembly constituting a stator coil in the statorof the automotive alternator according to Embodiment 3 of the presentinvention, FIG. 20B is a plan of the winding assembly constituting thestator coil in the stator of the automotive alternator according toEmbodiment 3 of the present invention, FIG. 21 is a perspective of partof a strand of wire constituting the stator coil in the stator of theautomotive alternator according to Embodiment 3 of the presentinvention, and FIG. 22 is a diagram explaining an arrangement of thestrands of wire constituting the stator coil in the stator of theautomotive alternator according to Embodiment 3 of the presentinvention.

[0158] As shown in FIG. 21, each strand of wire 61 constituting part ofthe winding assemblies 60 is formed into a planar pattern in whichstraight portions 61 b connected by turn portions 61 a are lined up at apitch of six slots (6P). Adjacent straight portions 61 b are offset by adistance equal to one width (W) of the strands of wire 61 and are linkedby the turn portions 61 a. As shown in FIG. 22, two strands of wire 61formed in the above pattern are offset by a pitch of six slots andarranged such that straight portions 61 b thereof overlap to constitutea wire-strand pair. As shown in FIGS. 20A and 20B, the windingassemblies 60 are constructed by arranging six wire-strand pairsarranged in the above manner so as to be offset by a pitch of one slotfrom each other. Six end portions of the strands of wire 61 each extendoutwards from first and second sides at first and second ends of thewinding assemblies 60. Furthermore, the turn portions 61 a whichconstitute the coil ends are arranged so as to line up in rows on firstand second side portions of the winding assemblies 60.

[0159] The two winding assemblies 60 constructed in this manner areinstalled into the stator core 50 in two rows radially and each of thestrands of wire 61 are joined so as to adopt the predetermined windingconstruction. The turn portions 61 a of the strands of wire 61 extendingoutwards and folded over at end surfaces of the stator core 50 form thecoil ends. The turn portions 61 a which are formed into a substantiallyidentical shape at both axial ends of the stator core 50 are mutuallyspaced circumferentially and radially, and arranged neatly in two rowscircumferentially to form the front-end and rear-end coil end groups 51f and 51 r.

[0160] The winding assemblies 60 can be prepared by arranging 12 strandsof the continuous wire, for example, at a pitch of one slot in a planeand simultaneously folding the twelve strands of continuous wire into alightning-bolt shape in the plane, then folding the strands upperpendicularly using a jig. At this time, crossover connections, outputwires, and neutral-point leads (not shown) are formed on the first andsecond side portions of the winding assemblies 60 by pulling out onlypredetermined strands of the continuous wire when the twelve strands ofwire are being folded into the lightning-bolt shape.

[0161] Next, the winding construction of one stator winding phaseportion 54 will be explained in detail with reference to FIG. 23.Moreover, in FIG. 23, the wiring at the rear end of the stator core 50is indicated by solid lines, and the wiring at front end by brokenlines.

[0162] One stator winding phase portion 54 is constituted by first tofourth winding sub-portions 62 to 65 each composed of one strand of wire61. The first winding sub-portion 62 is constructed into a wave windingin which one strand of wire 61 alternately occupies a first positionfrom an inner circumferential side (a first address) and a secondposition from the inner circumferential side (a second address) insidethe slots 50 b in every sixth slot from Slot Numbers 1 to 91. The secondwinding sub-portion 63 is constructed into a wave winding in which astrand of wire 61 alternately occupies the second address and the firstaddress inside the slots 50 b in every sixth slot from Slot Numbers 1 to91. The third winding sub-portion 64 is constructed into a wave windingin which a strand of wire 61 alternately occupies a third position fromthe inner circumferential side (a third address) and a fourth positionfrom the inner circumferential side (a fourth address) inside the slots50 b in every sixth slot from Slot Numbers 1 to 91. The fourth windingsub-portion 65 is constructed into a wave winding in which a strand ofwire 61 alternately occupies the fourth address and the third addressinside the slots 50 b in every sixth slot from Slot Numbers 1 to 91.

[0163] Thus, the first to fourth winding sub-portions 62 to 65 eachconstitute a winding sub-portion having one turn in which one strand ofwire 61 is wound into every sixth slot 50 b so as to alternately occupyan inner layer and an outer layer in a slot depth direction. Fourstrands of wire 61 are arranged to line up radially in one row withineach slot 50 b with the longitudinal direction of their rectangularcross sections aligned in a radial direction.

[0164] At the rear end of the stator core 50, a first end portion 63 aof the second winding sub-portion 63 extending outwards from the secondaddress of Slot Number 1 and a second end portion 65 b of the fourthwinding subportion 65 extending outwards from the third address of SlotNumber 91 are joined, and in addition, a first end portion 65 a of thefourth winding sub-portion 65 extending outwards from the fourth addressof Slot Number 1 and a second end portion 63 b of the second windingsub-portion 63 extending outwards from the first address of Slot Number91 are joined to form a winding having two turns.

[0165] At the front end of the stator core 50, a first end portion 62 aof the first winding sub-portion 62 extending outwards from the firstaddress of Slot Number 1 and a second end portion 64 b of the thirdwinding subportion 64 extending outwards from the fourth address of SlotNumber 91 are joined, and in addition, a first end portion 64a of thethird winding sub-portion 64 extending outwards from the third addressof Slot Number 1 and a second end portion 62 b of the first windingsub-portion 62 extending outwards from the second address of Slot Number91 are joined to form a winding having two turns.

[0166] In addition, a portion of the strand of wire 61 of the thirdwinding sub-portion 64 extending outwards at the rear end of the statorcore 50 from the third address of Slot Number 61 and the fourth addressof Slot Number 67 is cut, and a portion of the strand of wire 61 of thefourth winding sub-portion 65 extending outwards at the rear end of thestator core 50 from the third address of Slot Number 67 and the fourthaddress of Slot Number 73 is also cut. A first cut end 64 c of the thirdwinding sub-portion 64 and a first cut end 65 c of the fourth windingsub-portion 65 are joined to form one stator winding phase portion 54having four turns connecting the first to fourth winding sub-portions 62to 65 in series.

[0167] Moreover, the joint portion between the first cut end 64 c of thethird winding sub-portion 64 and the first cut end 65 c of the fourthwinding sub-portion 65 becomes a crossover connection connectingportion, and a second cut end 64 d of the third winding sub-portion 64and a second cut end 65 d of the fourth winding sub-portion 65 become aneutral-point (N) and an output wire (O), respectively.

[0168] A total of six stator winding phase portions 54 are similarlyformed by offsetting by one slot at a time the slots 50 b into which thestrands of wire 61 are installed. Then, as shown in FIG. 24, threestator winding phase portions 54 are connected into each of two starconnections to form the two three-phase stator winding groups 53. Eachof the three-phase stator winding groups 53 is connected to its ownrectifier 12, and the rectifiers 12 are connected in parallel so thatthe direct-current output from each is combined.

[0169] Thus, the strands of wire 61 constituting the first to fourthwinding sub-portions 62 to 65 are each wound into a wave winding so asto extend out of first slots 50 b at end surfaces of the stator core 50,fold back, and enter second slots 50 b six slots away. Each of thestrands of wire 61 is wound so as to alternately occupy the inner layerand the outer layer relative to the slot depth direction (the radialdirection) in every sixth slot. The first winding sub-portions 62 andthe second winding sub-portions 63 are inversely wound and offset by anelectrical angle of 180° relative to each other and constitute the firstwinding assembly 60. Similarly, the third winding sub-portions 43 andthe fourth winding sub-portions 44 are inversely wound and offset by anelectrical angle of 180° relative to each other and constitute thesecond winding assembly 60.

[0170] Embodiment 3 is constructed similarly to Embodiment 1 aboveexcept for the fact that the stator 81 is used in place of the stator 8.Thus, the overall cooling efficiency can be raised further and noise canbe significantly decreased in Embodiment 3 as well by adopting theconstructions from any of Inventive Examples 1 to 9 above.

[0171] Furthermore, the axial height of the turn portions 61 aconstituting the front-end coil end group may be made greater than theaxial height of the turn portions 61 a in the rear-end coil end group.In that case, the volume of the coil end group exposed to the coolingair flow is limited in the rear end, where cooling efficiency is poor,and the volume of the coil end group exposed to the cooling air flow isincreased in the front end, where cooling efficiency is good, coolingthe stator coil 51 effectively.

[0172] According to Embodiment 3, the stator coil 51 is constructed bylinking six stator winding phase portions 54 to form two three-phasestator winding groups 53. Each of the stator winding phase portions 54is constructed from one strand of wire 61 constituted by a large numberof straight portions 61 b housed inside the slots 50 b and a largenumber of turn portions 61 a linking together end portions of adjacentstraight portions 61 b outside the slots 50 b by housing the straightportions 61 b in every sixth slot 50 b so as to occupy different layersrelative to a slot depth direction. Thus, in Embodiment 3, the number ofjoints in the stator coil is significantly reduced compared toEmbodiment 1 in which a large number of U-shaped coil segments 30 wereused, enabling the productivity of the stator to be improved, andsoftening of the electrical conductors due to welding is eliminated,improving the rigidity of the stator, thereby enabling reducing magneticnoise to be reduced.

[0173] Moreover, in Embodiment 3 above, one strand of wire 61 is woundinto a wave winding having one turn per lap so as to alternately occupydifferent layers in every sixth slot, but the winding construction ofthe strand of wire is not limited to this; one strand of wire may bewound into a lap winding having two turns per lap so as to alternatelyoccupy different layers in every sixth slot, for example.

[0174] Each of the above embodiments uses coil segments 30 and strandsof wire 61 having a rectangular cross section, but the coil segments andstrands of wire are not limited to a rectangular cross section; they mayhave a circular cross section, or a portion of coil segments or strandsof wire having a circular cross section may be formed with a rectangularcross section.

[0175] In each of the above embodiments, the slots 15 b (50 b) aredisposed at an even pitch, but it is not necessary to dispose the slots15 b (50 b) at an even pitch; they may be disposed at an uneven pitch.

[0176] As shown in FIG. 2, in each of the above embodiments, thecapacity (air flow pressure) of the rear-end fan is greater than thecapacity of the front-end fan at all air flow rate points, but inpractice, the capacity (air flow pressure) of the rear-end fan onlyneeds to be greater than the capacity of the front-end fan in theworking air flow region of the automotive alternator. Furthermore, it isnot necessary to maintain this relationship for all rotationalfrequencies; the fans may be set to satisfy this relationship inrotational frequency regions where temperature and wind noise are aproblem.

[0177] The present invention is constructed in the above manner andexhibits the effects described below.

[0178] According to one aspect of the present invention, there isprovided an automotive alternator including:

[0179] In order to achieve the above object, according to one aspect ofthe present invention, there is provided an automotive alternatorincluding:

[0180] a rotor fastened to a shaft rotatably supported by a frontbracket and a rear bracket, the rotor having a pair of Lundell-type polecores disposed inside the brackets;

[0181] a stator supported by the brackets, the stator being disposed soas to cover an outer circumference of the rotor, the stator comprising:

[0182] a cylindrical stator core in which a plurality of slots havinggrooves lying in an axial direction are disposed circumferentially so asto open onto an inner circumferential side; and

[0183] a stator coil installed in the stator core so as to constitute apredetermined winding construction;

[0184] a pulley fastened to a front end of the shaft; and

[0185] a rectifier disposed at a rear end of the rotor,

[0186] wherein

[0187] a plurality of front-end and rear-end air intake apertures aredisposed in axial end surfaces of the front and rear brackets,respectively;

[0188] a plurality of front-end and rear-end air discharge apertures aredisposed in radial side surfaces of the front and rear brackets,respectively; and

[0189] front-end and rear-end blowing means are disposed at front andrear axial ends of the rotor, respectively,

[0190] whereby a front-end ventilation pathway in which a cooling airflow flows through the front-end air intake apertures into the front-endbracket and flows out through the front-end air discharge apertures, arear-end ventilation pathway in which a cooling air flow flows throughthe rear-end air intake apertures into the rear-end bracket and flowsout through the rear-end air discharge apertures, and a front-to-rearventilation pathway in which a cooling air flow flows through an innerside of the rotor between the front end and the rear end each isgenerated by operation of the blowing means,

[0191] wherein a capacity of the rear-end blowing means is greater thana capacity of the front-end blowing means, and a front-end air intakeflow rate is greater than a rear-end air intake flow rate, improvingcooling efficiency by the cooling air flow, thereby providing anautomotive alternator enabling the temperature of the stator coil andthe rectifier to be lowered and also enabling worsening of wind noise tobe suppressed.

[0192] A front-end air discharge flow rate may be greater than arear-end air discharge flow rate, further improving cooling efficiencyby the cooling air flow, thereby reliably enabling the temperature ofthe stator coil and the rectifier to be lowered.

[0193] According to another aspect of the present invention, there isprovided an automotive alternator including:

[0194] a rotor fastened to a shaft rotatably supported by a frontbracket and a rear bracket, the rotor having a pair of Lundell-type polecores disposed inside the brackets;

[0195] a stator supported by the brackets, the stator being disposed soas to cover an outer circumference of the rotor, the stator comprising:

[0196] a cylindrical stator core in which a plurality of slots havinggrooves lying in an axial direction are disposed circumferentially so asto open onto an inner circumferential side; and

[0197] a stator coil installed in the stator core so as to constitute apredetermined winding construction;

[0198] a pulley fastened to a front end of the shaft; and

[0199] a rectifier disposed at a rear end of the rotor,

[0200] wherein

[0201] a plurality of front-end and rear-end air intake apertures aredisposed in axial end surfaces of the front and rear brackets,respectively;

[0202] a plurality of front-end and rear-end air discharge apertures aredisposed in radial side surfaces of the front and rear brackets,respectively; and

[0203] front-end and rear-end blowing means are disposed at front andrear axial ends of the rotor, respectively,

[0204] whereby a front-end ventilation pathway in which a cooling airflow flows through the front-end air intake apertures into the front-endbracket and flows out through the front-end air discharge apertures, arear-end ventilation pathway in which a cooling air flow flows throughthe rear-end air intake apertures into the rear-end bracket and flowsout through the rear-end air discharge apertures, and a front-to-rearventilation pathway in which a cooling air flow flows through an innerside of the rotor between the front end and the rear end each isgenerated by operation of the blowing means,

[0205] wherein a capacity of the rear-end blowing means is greater thana capacity of the front-end blowing means, and a front-end air dischargeflow rate is greater than a rear-end air discharge flow rate, improvingcooling efficiency by the cooling air flow, thereby providing anautomotive alternator enabling the temperature of the stator coil andthe rectifier to be lowered and also enabling worsening of wind noise tobe suppressed.

[0206] The front-to-rear ventilation pathway may be blocked, increasingthe front-end air discharge flow rate, thereby enabling temperatureincreases in the stator coil to be further suppressed.

[0207] The front-end and rear-end blowing means may be the Lundell-typepole cores or fans, enabling front-end and rear-end ventilation pathwaysto be formed in which cooling air flows flow axially into the front andrear brackets and are later expelled radially from the front and rearbrackets.

[0208] The front-end blowing means may be one of the Lundell-type polecores and the rear-end blowing means may be a fan, enabling costs to belowered.

[0209] The front-end and rear-end blowing means may be fans, each fancomprising:

[0210] a generally annular fan base portion;

[0211] a plurality of blade base plates extending radially outwards fromouter circumferential edge portions of the fan base portion; and

[0212] a plurality of blades standing on an outer circumferential edgeportion of each of the plurality of blade base plates, enabling blowingcapacity to be increased, thereby raising cooling performance.

[0213] The rear-end fan may be provided with a greater number of bladesthan the front-end fan, enabling the capacity of the rear-end fan to bemade greater than that of the front-end fan.

[0214] A maximum blade height of the rear-end fan may be greater than amaximum blade height of the front-end fan, enabling the capacity of therear-end fan to be made greater than that of the front-end fan.

[0215] The blade base plates of the rear-end fan may be formed into ashape which blocks valley portions between adjacent magnetic poles ofthe rotor, increasing the capacity of the rear-end fan and lowering thefront-to-rear flow rate of the cooling air, thereby enabling coolingperformance to be improved.

[0216] A shielding plate may be disposed for blocking air gaps formed bythe blade base plates of the rear-end fan and valley portions betweenadjacent magnetic poles of the rotor, increasing the capacity of therear-end fan and lowering the front-to-rear flow rate of the coolingair, thereby enabling cooling performance to be improved.

[0217] The stator coil may be constructed by:

[0218] inserting coil segments composed of short conductors formed intoa general U shape from a first end of the stator core into slot pairs inwhich the slots in each pair are a predetermined number of slots apart;and

[0219] circumferentially bending and joining together free end portionsof the coil segments extending outwards at a second end of the statorcore from slots the predetermined number of slots apart so as toconstitute the predetermined winding construction,

[0220] wherein turn-end coil ends formed by U-shaped turn ends of thecoil segments are aligned in rows circumferentially to constitute aturn-end coil end group, and joint-end coil ends formed by the joiningof the free end portions of the coil segments are aligned in rowscircumferentially to constitute a joint-end coil end group, enabling thestator coil to be constructed simply.

[0221] The joint-end coil end group of the stator coil may be disposedat the front end of the stator core, enabling the stator coil to becooled effectively.

[0222] The stator coil may be constructed by linking a plurality ofwinding sub-portions so as to constitute the predetermined windingconstruction,

[0223] wherein each of the winding sub-portions is constituted by onestrand of wire constituted by a large number of straight portions housedinside the slots and a large number of turn portions linking togetherend portions adjacent straight portions outside the slots, the strand ofwire being installed in the stator core by housing the straight portionsso as to form different layers relative to a slot depth direction inslots the predetermined number of slots apart, and coil ends formed bythe turn portions are aligned in rows circumferentially to constitutefront-end and rear-end coil end groups of the stator coil, enabling thenumber of joints in the stator coil to be significantly reduced, therebyenabling the productivity of the stator to be improved, and eliminatingsoftening of the electrical conductors due to welding, thereby improvingthe rigidity of the stator and enabling reducing magnetic noise to bereduced.

[0224] The foregoing description of the preferred embodiments of theinvention has been presented for purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise from disclosed, and modifications andvariations are possible in light of the above teachings or may beacquired from practice of the invention. The embodiments ware chosen anddescribed in order to explain the principles of the invention and itspractical application to enable one skilled in the art to utilize theinvention in various embodiments and with various modifications as aresuited to the particular use contemplated. It is intended that the scopeof the invention be defined by the claims appended hereto, and theirequivalents.

What is claimed is:
 1. An automotive alternator comprising: a rotorfastened to a shaft rotatably supported by a front bracket and a rearbracket, said rotor having a pair of Lundell-type pole cores disposedinside said brackets; a stator supported by said brackets, said statorbeing disposed so as to cover an outer circumference of said rotor, saidstator comprising: a cylindrical stator core in which a plurality ofslots having grooves lying in an axial direction are disposedcircumferentially so as to open onto an inner circumferential side; anda stator coil installed in said stator core so as to constitute apredetermined winding construction; a pulley fastened to a front end ofsaid shaft; and a rectifier disposed at a rear end of said rotor,wherein a plurality of front-end and rear-end air intake apertures aredisposed in axial end surfaces of said front and rear brackets,respectively; a plurality of front-end and rear-end air dischargeapertures are disposed in radial side surfaces of said front and rearbrackets, respectively; and front-end and rear-end blowing means aredisposed at front and rear axial ends of said rotor, respectively,whereby a front-end ventilation pathway in which a cooling air flowflows through said front-end air intake apertures into said front-endbracket and flows out through said front-end air discharge apertures, arear-end ventilation pathway in which a cooling air flow flows throughsaid rear-end air intake apertures into said rear-end bracket and flowsout through said rear-end air discharge apertures, and a front-to-rearventilation pathway in which a cooling air flow flows through an innerside of said rotor between said front end and said rear end each isgenerated by operation of said blowing means, wherein a capacity of saidrear-end blowing means is greater than a capacity of said front-endblowing means, and a front-end air intake flow rate is greater than arear-end air intake flow rate.
 2. The automotive alternator according toclaim 1 wherein a front-end air discharge flow rate is greater than arear-end air discharge flow rate.
 3. The automotive alternator accordingto claim 1 wherein said front-to-rear ventilation pathway is blocked. 4.The automotive alternator according to claim 1 wherein said front-endand rear-end blowing means are said Lundell-type pole cores or fans. 5.The automotive alternator according to claim 1 wherein: said front-endblowing means is one of said Lundell-type pole cores; and said rear-endblowing means is a fan.
 6. The automotive alternator according to claim1 wherein said front-end and rear-end blowing means are fans, each fancomprising: a generally annular fan base portion; a plurality of bladebase plates extending radially outwards from outer circumferential edgeportions of said fan base portion; and a plurality of blades standing onan outer circumferential edge portion of each of said plurality of bladebase plates.
 7. The automotive alternator according to claim 6 whereinsaid rear-end fan is provided with a greater number of blades than saidfront-end fan.
 8. The automotive alternator according to claim 6 whereina maximum blade height of said rear-end fan is greater than a maximumblade height of said front-end fan.
 9. The automotive alternatoraccording to claim 6 wherein said blade base plates of said rear-end fanare formed into a shape which blocks valley portions between adjacentmagnetic poles of said rotor.
 10. The automotive alternator according toclaim 6 wherein a shielding plate is disposed for blocking air gapsformed by said blade base plates of said rear-end fan and valleyportions between adjacent magnetic poles of said rotor.
 11. Theautomotive alternator according to claim 1 wherein said stator coil isconstructed by: inserting coil segments composed of short conductorsformed into a general U shape from a first end of said stator core intoslot pairs in which said slots in each pair are a predetermined numberof slots apart; and circumferentially bending and joining together freeend portions of said coil segments extending outwards at a second end ofsaid stator core from slots the predetermined number of slots apart soas to constitute the predetermined winding construction, whereinturn-end coil ends formed by U-shaped turn ends of said coil segmentsare aligned in rows circumferentially to constitute a turn-end coil endgroup, and joint-end coil ends formed by said joining of said free endportions of said coil segments are aligned in rows circumferentially toconstitute a joint-end coil end group.
 12. The automotive alternatoraccording to claim 11 wherein said joint-end coil end group of saidstator coil is disposed at said front end of said stator core.
 13. Theautomotive alternator according to claim 1 wherein said stator coil isconstructed by linking a plurality of winding sub-portions so as toconstitute the predetermined winding construction, wherein each of saidwinding sub-portions is constituted by one strand of wire constituted bya large number of straight portions housed inside said slots and a largenumber of turn portions linking together end portions adjacent straightportions outside said slots, said strand of wire being installed in saidstator core by housing said straight portions so as to form differentlayers relative to a slot depth direction in slots the predeterminednumber of slots apart, and coil ends formed by said turn portions arealigned in rows circumferentially to constitute front-end and rear-endcoil end groups of said stator coil.
 14. An automotive alternatorcomprising: a rotor fastened to a shaft rotatably supported by a frontbracket and a rear bracket, said rotor having a pair of Lundell-typepole cores disposed inside said brackets; a stator supported by saidbrackets, said stator being disposed so as to cover an outercircumference of said rotor, said stator comprising: a cylindricalstator core in which a plurality of slots having grooves lying in anaxial direction are disposed circumferentially so as to open onto aninner circumferential side; and a stator coil installed in said statorcore so as to constitute a predetermined winding construction; a pulleyfastened to a front end of said shaft; and a rectifier disposed at arear end of said rotor, wherein a plurality of front-end and rear-endair intake apertures are disposed in axial end surfaces of said frontand rear brackets, respectively; a plurality of front-end and rear-endair discharge apertures are disposed in radial side surfaces of saidfront and rear brackets, respectively; and front-end and rear-endblowing means are disposed at front and rear axial ends of said rotor,respectively, whereby a front-end ventilation pathway in which a coolingair flow flows through said front-end air intake apertures into saidfront-end bracket and flows out through said front-end air dischargeapertures, a rear-end ventilation pathway in which a cooling air flowflows through said rear-end air intake apertures into said rear-endbracket and flows out through said rear-end air discharge apertures, anda front-to-rear ventilation pathway in which a cooling air flow flowsthrough an inner side of said rotor between said front end and said rearend each is generated by operation of said blowing means, wherein acapacity of said rear-end blowing means is greater than a capacity ofsaid front-end blowing means, and a front-end air discharge flow rate isgreater than a rear-end air discharge flow rate.
 15. The automotivealternator according to claim 14 wherein said front-end and rear-endblowing means are fans, each fan comprising: a generally annular fanbase portion; a plurality of blade base plates extending radiallyoutwards from outer circumferential edge portions of said fan baseportion; and a plurality of blades standing on an outer circumferentialedge portion of each of said plurality of blade base plates.
 16. Theautomotive alternator according to claim 15 wherein said rear-end fan isprovided with a greater number of blades than said front-end fan. 17.The automotive alternator according to claim 15 wherein a maximum bladeheight of said rear-end fan is greater than a maximum blade height ofsaid front-end fan.
 18. The automotive alternator according to claim 15wherein said blade base plates of said rear-end fan are formed into ashape which blocks valley portions between adjacent magnetic poles ofsaid rotor.
 19. The automotive alternator according to claim 15 whereina shielding plate is disposed for blocking air gaps formed by said bladebase plates of said rear-end fan and valley portions between adjacentmagnetic poles of said rotor.